Ephemeris: 04/24/2026 – Where did the lunar “seas” come from?

April 24, 2026 Comments off

This is Bob Moler with Ephemeris for Arbor Day, Friday, April 24th. Today the Sun will be up for 13 hours and 55 minutes, setting at 8:39, and it will rise tomorrow at 6:41. The Moon, 1 day past first quarter, will set at 4:08 tomorrow morning.

The face of the Moon is a bit more than half uncovered from our point of view, with first quarter occurring yesterday. It shows the string of lunar seas, those gray areas on the Moon which lead to the terminator, the Moon’s sunrise line. There is a larger sea called the Ocean of Storms on the eastern side of the Moon, as we see it. Most were created about 3.8 to 3.9 billion years ago by asteroid strikes. The same collisions happened to the Earth, but plate tectonics destroyed the evidence. Not so on the Moon. Many planetary scientists think it was the result of the Late Heavy Bombardment, caused by the changing orbits of mainly Saturn, Uranus and Neptune disrupting the asteroids, and sending them careening through the solar system.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Lunar seas
Lunar seas and their ages. (b.y. = billion years ago) Credit NASA.
Nice model of solar system evolution infographic
Nice model infographic: Evolution of the solar system. Step 6, with the exchange of Neptune’s and Uranus’ orbits, cause the Late Heavy Bombardment. The Nice model isn’t that nice. It’s named for Nice, France, the city where the model was first developed. Click or tap on the image to enlarge it. Credit: Nora Eisner
Categories: Ephemeris Program, The Moon Tags: ,

Ephemeris: 04/23/2026 – Where did the Moon come from?

April 23, 2026 Comments off

This is Ephemeris for Thursday, April 23rd. Today the Sun will be up for 13 hours and 52 minutes, setting at 8:37, and it will rise tomorrow at 6:43. The Moon, at first quarter today, will set at 3:42 tomorrow morning.

When one gazes upon the moon tonight the thought of where the moon came from might come to mind. Did it form with the Earth? Was it captured by the Earth? The latest thinking on the origin of the moon centers around a grazing collision with the Earth of a Mars sized body that has been given the name Theia, the mother of Selene, the goddess of the Moon, shortly after the Earth was formed. This is based on Apollo mission discoveries that the composition of the rocks on the moon are approximately the same as those of Earth’s crust. It’s been known for a while that there are two dense masses within the Earth about halfway to the center. One geologist has put forth that these masses could have been the core of Theia that sank into the Earth.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Collision spawning the Moon
The hypothetical collision of a Mars sized body with the young Earth. Credit: Joe Tucciarone via NASA
New moon formation
A new simulation on how the Moon formed. Credit: PBS.
Categories: Ephemeris Program, Origins Tags: , ,

Ephemeris: 04/22/2026 – Taking our weekly look at the whereabouts of the naked-eye planets

April 22, 2026 Comments off

This is Ephemeris for Earth Day, Wednesday, April 22nd. Today the Sun will be up for 13 hours and 50 minutes, setting at 8:36, and it will rise tomorrow at 6:45. The Moon, 1 day before first quarter, will set at 3:07 tomorrow morning.

Let’s take our weekly look at the whereabouts of the naked-eye planets. By 9 PM tonight or about 30 minutes or so after sunset, Venus may be seen very low in the West. A telescope will show a very tiny disc on Venus, because it is still pretty much beyond the Sun, 138 million miles (222 million kilometers) away from us. Over the next 6 months it will be moving closer to us and becoming much larger. Jupiter is the brilliant star-like object high in the west-southwestern sky before 10 PM. It will appear just below the crescent Moon tonight. Venus will set at 10:54, while Jupiter will hold out until 2:30 AM. Meanwhile, Mercury, Mars and Saturn are still bunched up just west of the Sun, but are overwhelmed by bright morning twilight.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Jupiter, and Venus with the Moon and Sirius at 9 PM tonight.
Jupiter, and Venus with the Moon and Sirius at 9 PM tonight, April 22, 2026. Created using Stellarium.
A closer look at Jupiter and the Moon at 9 PM tonight.
A closer look at Jupiter and the Moon at 9 PM tonight, April 22, 2026. Created using Stellarium.
The Moon, a day before first quarter, as seen at 9:30 PM tonight, April 22, 2026. A view visible in small telescopes showing an image with and without selected features labeled. Created using Stellarium, LibreOffice Draw, and GIMP.
Telescopic Jupiter and Venus (north up) as they would be seen in a small telescope with the same magnification.
Telescopic Jupiter and Venus (north up) as they would be seen in a small telescope with the same magnification. Venus will be visible for a short time near the western horizon, while Jupiter is visible most of the night. Venus’ apparent diameter will be 11.3″, and be 89.7% illuminated. It’s on the far side of the Sun, 1.5 times the Sun’s distance from us. Jupiter will be 36.4″ in diameter, with its moons shown here for 9:30 PM, tonight April 22, 2026. The moons can shift noticably over an hour, especially Io and Europa. The (”) symbol means seconds of arc, or 1/3600th of a degree. Created using Cartes du Ciel (Sky Charts), LibreOffice Draw and GIMP.
The naked-eye planets at sunset and sunrise on a single night, starting with sunset on the right on April 22, 2026. The night ends on the left with sunrise on the 22nd.
The naked-eye planets at sunset and sunrise on a single night, starting with sunset on the right on April 22, 2026. The night ends on the left with sunrise on the 22nd. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
A low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow.
This is a low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow, April 22 and 23rd, 2026. Some of the columns are self-explanatory, others are not. The transit column is the time that the body crosses the meridian and is due south. Elong, for elongation, is the angle between the Sun and that body. RA is right ascension, which is the object’s east-west position on the celestial sphere in hours and minutes. Dec is declination which is the north-south position of the object on the celestial sphere in degrees and minutes. R is the distance of that object from the Sun in astronomical units. An astronomical unit is about 93 million miles or 150 million kilometers. And Delta is the distance of that object from the Earth, also in astronomical units. I omit the ‘m’ in am and pm for compactness. The data was generated using my LookingUp for DOS app and displayed as a table by my Ephemeris Helper app.

Categories: Ephemeris Program, Naked-eye planets, Observing Tags: , , , , ,

Ephemeris: 04/21/2026 – The Lyrid meteor shower reaches its peak tomorrow

April 21, 2026 Comments off

This is Ephemeris for Tuesday, April 21st. Today the Sun will be up for 13 hours and 47 minutes, setting at 8:35, and it will rise tomorrow at 6:46. The Moon, 2 days before first quarter, will set at 2:21 tomorrow morning.

The second major meteor shower this year will reach its peak tomorrow afternoon around 3 PM (~19h UT). The best time to see it will be tomorrow morning after moonset at 2:21 AM. Astronomical twilight will begin to interfere after 5 AM. The other is tomorrow night starting 45 minutes later. The meteor shower is called the Lyrids, because they seem to come from near the constellation Lyra the harp and the bright star Vega. By 3 AM Vega will be high in the east. The radiant of the meteors is to the west of Vega, between Lyra and the dim constellation of Hercules. Though a major shower, the peak hourly rate is expected to be about 20 meteors an hour.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Lyrid meteor radiant.
Lyrid meteor radiant (LyrR) is near Lyra and the bright star Vega. The bright star by “Lyr” is Vega. Create by my LookingUp app.
Categories: Ephemeris Program, Meteor Shower, Observing Tags: , ,

Ephemeris: 04/20/2026 – A seeming convergence of planets too close to the Sun to be seen from Michigan

April 20, 2026 Comments off

This is Ephemeris for Monday, April 20th. Today the Sun will be up for 13 hours and 44 minutes, setting at 8:34, and it will rise tomorrow at 6:48. The Moon, halfway from new to first quarter, will set at 1:20 tomorrow morning.

There’s a close planetary alignment this happening and today in the morning sky that we can’t see, of Mercury Mars and Saturn which are too close to the sun, and the time of year is not the best for seeing them. So they’re invisible to us but visible for folks in the Southern Hemisphere. Even the Artemis 2 astronauts talked about them when they went into solar eclipse on their trip around the moon. But the action is all happening yesterday and today. As of last Friday they were, from left to right, Saturn Mars and Mercury. As of today it’s almost a vertical arrangement with Mars on top Saturn in the middle and Mercury on the bottom and by tomorrow it will be Mercury on the bottom Venus on the top and Saturn off to the right.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

The apparent convergence of three naked eye planets.
The apparent convergence of three naked eye planets which are invisible from our location in Northern Michigan, as being too close to the Sun and lost in morning twilight. Folks in the Southern Hemisphere may get a better view of it. This animation steps from April 16th through the 22nd at one day intervals, centered on Mars, as the planets Saturn and Mercury slowly switch places with respect to it. This image has an equatorial orientation with north directly up and west to the right. The orientation in the sky will be tilted about 45° to the left. Created using Stellarium and GIMP.
Categories: Conjunction, Ephemeris Program, Naked-eye planets, Planetrary grouping, Twilight Tags: , ,

Ephemeris: 04/17/2026 – The Moon’s Far Side isn’t dark!

April 17, 2026 Comments off

This is Bob Moler with Ephemeris for Friday, April 17th. Today the Sun will be up for 13 hours and 35 minutes, setting at 8:30, and it will rise tomorrow at 6:53. The Moon is new today, and won’t be visible.

When I hear discussions about the Artemis 2 missions, some people who ought to know better still refer to the far side of the moon as the dark side. Officially we have the two faces of the moon: the near side and the far side. I’ll even accept front side and back side. Until 1959 no one had ever seen the far side of the moon so it was dark, in the sense that we could not see it. Not dark because of the lack of light. I’ve been thinking about it. The far side sees more light from the sun, so maybe we should call it the bright side. It certainly has fewer maria or seas, those dark patches that we see on the near side of the Moon. There’s only one on the far side, it’s called the Moscow Sea since the Russian spotted first. Mare Orientale, subject of much study by the Artemis 2 crew, straddles the near side-far side line. It’s closer to the sun when it’s fully illuminated than the near side by about half a million miles, and it doesn’t suffer solar eclipses to darken it like the near side, being already in night, like it always is, at full moon.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Photograph of the crescent Earth setting behind the limb of the Moon by the Artemis 2 crew.
The far side may seem to be the dark side in this photograph of earthset by the Artemis 2 crew. It is as bright as the brightest parts of the near side. These are the crater filled highlands, so it is the exact same brightness as the highlands on the near side. And indeed in traveling to the Moon, when it was seen half near side and half far side, there was no difference in the brightness of the highlands between the two. So the moon is really dark gray in brightness, on average. It reflects something like 12% of the sunlight it receives, while the earth is more than twice that reflectance. Astronomers call that quantity albedo. So the Moon has an albedo of 12% while the Earth has an albedo of something like 29% on average. So the reason the full moon is so bright at night is due to lack of competition from something that’s actually much whiter. Credit: NASA/ESA/CSA -The Artemis 2 crew.
Categories: Astronomical fact, The Moon Tags: ,

Ephemeris: 04/16/2026 – The greatest distance humans have traveled from the Earth

April 16, 2026 Comments off

This is Ephemeris for Thursday, April 16th. Today the Sun will be up for 13 hours and 32 minutes, setting at 8:29, and it will rise tomorrow at 6:54. The Moon, 1 day before new, will rise at 6:38 tomorrow morning.

On their trip around the moon the Artemis 2 crew set a new record for distance from the earth of 252,760 miles (406,778 kilometers) which beat by 4,105 miles (6,607 kilometers) the record of Apollo 13 of 248,655 miles (400,171 kilometers). This was helped a great deal by the fact that the moon reached apogee, its farthest distance from the Earth, a few hours after the Artemis 2 capsule, Integrity, passed by. So I think the record is going to hold up for a while. So the only way to get further away from the earth is to head out to Mars, or the Chinese make a farther flyby of the Moon. The Artemis 2 mission was to see if the capsule can sustain human life comfortably during an extended mission. It seemed proved it’s worth. The videos that came back seem to be reasonably roomy, much more so than the Apollo capsule.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

At the time the spacecraft Integrity encountered the Moon, it was 4% farther away than average. Integrity was two moon diameters past the Moon at it's farthest from the Earth.
At the time the spacecraft Integrity encountered the Moon, it was 4% farther away than average. Integrity was two moon diameters past the Moon at it’s farthest from the Earth. Click or tap on the image to enlarge it.
Categories: Artemis Program, Ephemeris Program Tags:

Ephemeris: 04/15/2026 – Taking our weekly look at the whereabouts of the naked-eye planets

April 15, 2026 Comments off

This is Ephemeris for Wednesday, April 15th. Today the Sun will be up for 13 hours and 29 minutes, setting at 8:28, and it will rise tomorrow at 6:56. The Moon, 2 days before new, will rise at 6:15 tomorrow morning.

Let’s take our weekly look at the whereabouts of the naked-eye planets. By 9:15 PM tonight or about 45 minutes or so after sunset, Venus may be seen very low in the West. A telescope will show a very tiny disc on Venus, because it is still pretty much beyond the Sun, 141 million miles (226 million kilometers) away from us. Over the next 6 months it will be moving closer to us and becoming much larger. Jupiter is the brilliant star-like object high in the southwestern sky at the same time. Venus will set at 10:35, while Jupiter will hold out to 3 AM. Meanwhile, Mercury, Mars and Saturn are lined up just west of the Sun, but unfortunately are overwhelmed by bright morning twilight. Southern Hemisphere observers will them bunched up next week.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Jupiter and Venus with fading constellations of winter in the west at 9:30 PM.
Jupiter and Venus with fading constellations of winter at 9:30 PM tonight, April 15, 2026. Created using Stellarium.
Telescopic Jupiter and Venus as they would be seen in a small telescope with the same magnification (north up) as they would be seen in a small telescope with the same magnification.
Telescopic Jupiter and Venus as they would be seen in a small telescope with the same magnification (north up) as they would be seen in a small telescope with the same magnification at 9:30 PM tonight, April 15, 2026. Venus will be visible for a short time near the western horizon, while Jupiter is visible most of the night. Venus’ apparent diameter will be 11.1″, and be 91.2% illuminated. It’s on the far side of the Sun. Jupiter will be 37.1″ in diameter. Io will be behind Jupiter and in its shadow until 12:16 AM, when it will appear near Europa. The (”) symbol means seconds of arc, or 1/3600th of a degree. Created using Cartes du Ciel (Sky Charts), LibreOffice Draw and GIMP.
The naked-eye planets at sunset and sunrise on a single night, starting with sunset on the right on April 15, 2026. The night ends on the left with sunrise on the 16th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
A low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow.
This is a low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow, April 15 and 16th, 2026. Some of the columns are self-explanatory, others are not. The transit column is the time that the body crosses the meridian and is due south. Elong, for elongation, is the angle between the Sun and that body. RA is right ascension, which is the object’s east-west position on the celestial sphere in hours and minutes. Dec is declination which is the north-south position of the object on the celestial sphere in degrees and minutes. R is the distance of that object from the Sun in astronomical units. An astronomical unit is about 93 million miles or 150 million kilometers. And Delta is the distance of that object from the Earth, also in astronomical units. I omit the ‘m’ in am and pm for compactness. The data was generated using my LookingUp for DOS app and displayed as a table by my Ephemeris Helper app.

Categories: Ephemeris Program, Naked-eye planets, Observing Tags: , , , , ,

Ephemeris: 04/14/2026 – My virtual flight with the Artemis II crew

April 14, 2026 Comments off

This is Ephemeris for Tuesday, April 14th. Today the Sun will be up for 13 hours and 26 minutes, setting at 8:26, and it will rise tomorrow at 6:58. The Moon, 3 days before new, will rise at 5:55 tomorrow morning.

I hadn’t enjoyable time last week Monday afternoon listening to Artemis 2 astronauts talking with the science team on Earth about what they were seeing Moon’s far side. I have the program called Virtual Moon Atlas which allows one to see the entire Moon with the phase and shadows. And I was able to rotate it and get the phase right so it appeared pretty much as it did to the astronauts. So I was able to follow along with their discussions of the far side features that they were seeing and photographing. I could zoom in to craters and features they were talking about, but nowhere near the detail they were seeing. So I consider it to be a really great time of, in essence, flying along with the astronauts.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.

Addendum

A view of the Moon from the camera attached to the solar panel of the European Service Module of the Orion spacecraft looking at the moon and crossing over the sunrise terminator on the far side.
This is a view of the Moon from the camera attached to the solar panel of the European Service Module of the Orion spacecraft looking at the moon and crossing over the sunrise terminator on the far side. The resolution of the image in on YouTube was about half the resolution of this image. Obviously the photographs that were taken would not be downloaded in real time as the lower resolution version of this image was. Credit: NASA European Space Agency.
A view from the Virtual Moon Atlas (VMA) from the approximate viewpoint of the Orion spacecraft at the time of the image above, with increased contrast and rotated. Being closer to the moon than this image depicts the edge or limb of the moon or horizon is much closer than is shown here so Oceanus Procellarum is over their horizon. They mentioned the crater Vavilov a lot, but VMA requires exact spelling to point it out. Clicking on a crater will display its name. Vavilov happens to be a double crater, and eventually I clicked on it, and got its name… Russian, of course.

Categories: Adventures, Artemis Program, Ephemeris Program, The Moon Tags: ,

Ephemeris: 04/13/2026 – How the Greeks saw the constellation Leo

April 13, 2026 Comments off

This is Bob Moler with Ephemeris for Monday, April 13th. Today the Sun will be up for 13 hours and 23 minutes, setting at 8:25, and it will rise tomorrow at 7:00. The Moon, 3 days past last quarter, will rise at 5:35 tomorrow morning.

The constellations that we know are mostly those that come from the Sumerians and other civilizations who lived around what is now modern day Iraq. They were adopted and adapted by the ancient Greeks, and to us. Foremost of these was Leo the lion, seen high in the south-southeastern sky at 10 PM. It is easily found by imagining the bottom of the Big Dipper leaks. It will drip on the back of Leo, with its distinctive backward question mark as his front with his head and mane. To the Greeks he was the Nemean Lion, whose coat was impervious to arrows or spears. Heracles (Hercules) was able to kill it by first stunning it with a club then strangling it with his bare hands. It was the first of his Twelve Labors.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Leaky Dipper drips on Leo.
Leaky Big Dipper drips on Leo. Created using mu LookingUp program.
Hercules killing the Nemean Lion as the first of his Twelve Labors. An image generated by Google's AI.
Hercules killing the Nemean Lion as the first of his Twelve Labors. Image generated by Google’s Gemini AI (Nano Banana 2).
Categories: Constellations, Ephemeris Program, Mythology, Observing Tags: ,